Fix for Python 3.x in replace_more_comments()

There was a bug that made replace_more_comments() unusable for Python 3.x. In the` _extract_more_comments()` function a heap requires the ability to make a comparison. You did add the `__cmp__` function to the `MoreComments` class, but unfortunately `cmp()` has been gotten rid of in Python 3 and been replaced by `__lt__`. Anyway, there it is. You will probably understand it more if you just look at the code, I'm bad at explaining stuff. Anyway, enjoy!